89 lines
3.2 KiB
Groff
89 lines
3.2 KiB
Groff
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.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" * SPDX-License-Identifier: curl
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_DNS_CACHE_TIMEOUT 3 "17 Jun 2014" libcurl libcurl
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.SH NAME
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CURLOPT_DNS_CACHE_TIMEOUT \- life-time for DNS cache entries
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);
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.fi
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.SH DESCRIPTION
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Pass a long, this sets the timeout in seconds. Name resolve results are kept
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in memory and used for this number of seconds. Set to zero to completely
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disable caching, or set to -1 to make the cached entries remain forever. By
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default, libcurl caches this info for 60 seconds.
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We recommend users not to tamper with this option unless strictly necessary.
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If you do, be careful of using large values that can make the cache size grow
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significantly if many different host names are used within that timeout
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period.
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The name resolve functions of various libc implementations do not re-read name
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server information unless explicitly told so (for example, by calling
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\fIres_init(3)\fP). This may cause libcurl to keep using the older server even
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if DHCP has updated the server info, and this may look like a DNS cache issue
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to the casual libcurl-app user.
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DNS entries have a "TTL" property but libcurl does not use that. This DNS
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cache timeout is entirely speculative that a name resolves to the same address
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for a small amount of time into the future.
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Since version 8.1.0, libcurl prunes entries from the DNS cache if it exceeds
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30,000 entries no matter which timeout value is used.
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.SH DEFAULT
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60
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.SH PROTOCOLS
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All
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.SH EXAMPLE
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.nf
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
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/* only reuse addresses for a short time */
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curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 2L);
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ret = curl_easy_perform(curl);
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/* in this second request, the cache is not be used if more than
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two seconds have passed since the previous name resolve */
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ret = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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.fi
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.SH AVAILABILITY
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Always
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.SH RETURN VALUE
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Returns CURLE_OK
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.SH "SEE ALSO"
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.BR CURLOPT_CONNECTTIMEOUT_MS (3),
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.BR CURLOPT_DNS_SERVERS (3),
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.BR CURLOPT_DNS_USE_GLOBAL_CACHE (3),
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.BR CURLOPT_MAXAGE_CONN (3),
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.BR CURLOPT_RESOLVE (3)
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